The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component or line that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed. In one example associated with lithography patterning, a photomask (or mask) to be used in a lithography process has a circuit pattern defined thereon and is to be transferred to wafers. In advanced lithography technologies, an extreme ultraviolet (EUV) lithography process is implemented with a reflective mask. The reflective mask needs to be cleaned to make the mask defect free.
The cleanliness of a lithography mask is essential in the yield of the lithography process. Operating or transporting a mask in a completely particle-free clean room and exposure tool is impossible. In other words, certain level of environmental nano-scale or macro-scale particles, which mainly are induced during transportation, could be directly adhered on back-side or front-side of the mask, thereby diminishing the cleanness of mask and mask stage. As a result, the yield of the lithography production is suffered due to non-cleaning mask. Therefore, how to effectively clean mask featuring closely damage-free is one major topic in the lithography process. In one example, the existing cleaning processes may cause various damages to the mask, or have high manufacturing cost. In another example, the existing cleaning processes could not effectively remove nano-scale particles. In yet another example, the existing cleaning method is complicated and is associated with high cost tool. In yet another example, additional particles could be further induced during the existing cleaning procedure. There are no effective clean method and system in the EUV lithography process. Vacuum technique cannot be used to clean inside the EUV lithography system.
Therefore, what is needed is a system and method to address the above issues.